The paper describes experimental research of slab-column connections examined on specimendesigned as a part of reinforced concrete structure with flat slabs. The aim of the research wasto verify the efficiency of slab reinforcement concept against punching shear by increasing slab’smechanical reinforcement ratio by applying additional external reinforcement in the form of carbonfiber reinforced polymer (CFRP) strips. The capacity enhancement in comparison to unstrengthened slab obtained 36%.
Reinforced concrete composite slab consists of a thin prefabricated slab in which span reinforcement is located and of concrete joined with the slab, with such concrete being laid on site. The existence of a joint of two concretes in such floors is interpreted as introducing a contact layer into a monolithic slab. In the paper parameters of two models are estimated. The first is a model of a contact layer and the second is a model of a composite slab with a single degree of freedom. The models consider that the contact has elastic properties and inelastic properties causing energy dissipation. Experimental investigations are discussed further based on which the parameters values of the contact layer model were determined. Delamination was experienced for the slabs characterised by low contact layer stiffness after applying a maximum load. In addition, the strains of a contact layer having low stiffness are accompanied by lower energy dissipation than of a layer with high stiffness. The smaller stiffness of composite floors, as compared to monolithic floors, occurs as a consequence of the existence of a joint. Such decrease for a composite slab is interpreted in the model with a single degree of freedom as the serial connection of stiffness of a monolithic slab and an element considering the existence of a contact layer. The stiffness of an element considering the existence of a contact layer decreases along with a load, and the elements corresponding to the higher stiffness of the contact layer are characterised by higher energy dissipation. The aforementioned results of the investigations confirm the assumptions of the contact layer model and a composite slab model with a single degree of freedom. The findings made represent a basis for establishing a method of evaluating the condition of a joint in composite slabs according to statistical investigations.
The results of experimental test of nine thickset reinforced concrete slabs in punching are presented in the this paper. The aim of the tests was verifi cation of the Eurocode EC 2 procedure, by which the ultimate shear stresses vRd,c depend on the slenderness of the slab. Besides of the performed tests results, the analysis of the foreign investigation of the fundaments is also included. The test results, as well as other tests, show the correctness of the function assumed in Eurocode 2, which gives correlation between ultimate stresses vRd,c and shear slenderness.